In recent years, as a large number of semiconductor elements are highly integrated with each other and produced on a mass production line, research works have been positively conducted for developing a material employable for the semiconductor elements. In addition, it has been requested in many application fields that development works are conducted further with respect to each member for the semiconductor element in consideration of properties required for the material employable for the foregoing member and a cost level of the material.
For example, a Fe-Ni based alloy such as 42 wt % Ni-Fe, 29 wt % Ni-17 wt % Co-Fe or the like each having a thermal expansion coefficient approximate to that of the semiconductor elements has been hitherto used as a material for a lead frame used for a semiconductor package such an integrated circuit package or the like. Since expensive nickel and cobalt are used as alloy components for the iron based lead frame, there appear problems that lead frames are produced at a high cost, and an excellent property of heat radiation, i.e., excellent thermal conductivity, which is required as a number of semiconductor elements are highly integrated with each other, is not satisfactory. In view of the foregoing problems, a comparatively inexpensive copper alloy having an excellent property of heat radiation is being used as a material employable for lead frames at present. For example, a Cu-Sn based copper alloy, a Cu-Sn-Ni-Si based copper alloy, a Cu-Fe-P based copper alloy and a Cu-Sn-Ni-Si-Zn based copper alloy are used as a copper alloy employable for lead frames.
However, in a case where a plastic sealing type semiconductor package is constructed using a lead frame made of one of the aforementioned copper alloys, there arises a difficulty that a sufficiently excellent property of adhesiveness of the lead frame to a sealing plastic is hardly obtained. If the lead frame has poor adhesiveness to the sealing plastic, moisture resistance, weather resistance, erosion resistance or the like of an integrated circuit, a large scale integrated circuit or the like are affected adversely. Therefore, incorrect adhesion of the lead frame to the sealing plastic reduces reliability on an integrated circuit package, a large scale integrated circuit or the like.
For this reason, it has been strongly requested that a lead frame exhibiting an excellent property of adhesiveness to the sealing plastic is developed. In addition, it has been likewise intensely requested that a excellent reliable semiconductor package using the foregoing lead frame is developed.
The present invention has been made in consideration of the aforementioned background.
An object of the present invention is to provide a lead frame having an excellent property of adhesiveness to a sealing plastic.
Another object of the present invention is to provide a semiconductor package having an excellent reliability by using the foregoing lead frame having an excellent property of adhesiveness to a sealing plastic.